In Mark, U.S. Pat. No. 4,110,299, flame-retardant polycarbonate compositions are disclosed wherein the flame retardant comprises an organic monomeric or polymeric aromatic or heterocyclic halide. Also described are such compositions containing from 0.01 to 2.0 weight percent of a fluorinated polyolefin, e.g., poly(tetrafluoroethylene) to retard dripping flaming resin when articles molded from such compositions are exposed to an open flame. Although such compositions represent the current state of the art, dripping can still be a problem, especially in such impact modified compositions, particularly if the impact modifier is an acrylate polymer or copolymer, such as a copolymer of ethylene and ethyl acrylate.
Also showing the current state of the art is Rosenquist, U.S. Pat. No. 4,579,896, which discloses flame retardant and drip retardant polycarbonate compositions comprised of an aromatic carbonate resin, a flame retardant compound and a bis cyclic carbonate drip retardant.
In Calkins, U.S. Pat. No. 3,489,716 are disclosed aromatic polycarbonate resin compositions which do not include a flame retardant additive, but which are rendered color stable at elevated temperatures by adding 0.01 to 0.5 weight percent of an epoxidized cycloaliphatic compound. In Factor, U.S. Pat. No. 3,673,146, are disclosed color tinted polycarbonate compositions which do not increase in yellowness when remolded because they contain a small amount of a cycloaliphatic epoxy compound. In neither Calkins nor Factor is there any hint or suggestion that epoxidized cycloaliphatic compounds will function as drip-retarding agents in flame-retardant compositions.
It has now surprisingly been found that epoxidized cycloaliphatic compounds can be employed alone or together with other additives to render flame-retardant polycarbonate compositions free of any tendency after molding to drip flaming resins when exposed to an open flame, and exposure to humidity, and this discovery is the subject matter of the present invention.